Yeah it's pretty bone-headed to say Hong Kong is its own biggest source of pollution when mainland China's polluting almost equal amount (44%?) of days in a year.

But what's wrong with cleaning up the air in Hong Kong, when it's perfectly in a position to do? The reasoning is not convincing as you say. But it doesn't mean you shouldn't do it. Cleaning up China will take a whole different approach.

I'm loath to go back, especially during summer, partly because the air has become so unbreathable.

It may cost quite a bit and it might harm some industries. You sounded like the those advocating against the Kyoto Treaty here. It's gonna cost jobs! It's gonna destroy the economy! The thing is you don't realize a whole host of companies have poped up to serve the new green economy. Change happens.